Houseplant insects are so tiny that we often don't notice them when caring for our plants. It's only when they begin annoying us while reading and relaxing that we really begin to pay attention to them.
Houseplant insects find their way to your plants in numerous avenues. Some come indoors hiding in the soil of a plant brought in from outside for the winter. Others hide in the leaves and stems of plants given to you or purchased and brought home.
Early detection of pests on your plants will help you stop the problem using biological controls before the plant is harmed. If picking off the pests or repotting the plant in all new fresh soil doesn't work, try relatively harmless products such as insecticidal soap or oil. If that doesn't work, you may need to use a chemical pesticide designed just for houseplants.
Here are few of the more common houseplant pests and suggested treatments.
Aphids are tiny insects that suck on the tender parts of the plant. They are 1/8 inch long and pear-shaped, and you'll find them on the underside of the leaf. Stems, leaves and flower buds become distorted, weak and sticky. To get rid of aphids, try washing the insects off the plants with blast of water. If that doesn't work, chemical controls such as insecticidal soaps and dormant oils might be effective. Be sure to remove infected leaves, stems or flowers. Repeat treatment every seven to 10 days because aphids reproduce very quickly.
Fungus gnats, although usually harmless, can weaken a plant if the maggots in the soil begin eating the roots. They tend to be most problematic in soil that has been overwatered. Treatment is best handled by repotting the plant into a clean pot with fresh soil, taking care to not repot the eggs or larvae. If repotting is not an option, drench the soil with insecticide.
Scale insects infest the stems and veins on leaf undersides. Scale weakens your plant by sucking its sap and may kill the plant. The best mechanical control is to wipe off the scales with a damp cloth soaked in alcohol or spray with neem or horticultural oil.
Red Spider Mites may produce webbing on the leaves, which then will become speckled, turn yellow and fall off. Hot, dry conditions encourage these pests. The best mechanical control is to frequently wash off the leaves on both sides. This not only washes away the insect, but spider mites do not like humid conditions. You also might try insecticidal soaps and horticultural oils. Be sure to discard all dead foliage.
Tiny, mothlike whiteflies can be found on the underside of leaves, flying away when disturbed. They damage the plant by removing sap. Also, they leave sticky honeydew by product on plants that allow gray sooty mold to grow. Chemical controls include dormant oils, insecticidal soaps and pyrethrins.
Mealybugs are small, oval bugs that secrete a white cottony substance and form colonies on stems and leafstalks. To control mealybugs, wipe plants off with a cloth soaked in alcohol or spray with horticultural oil.